Late Pliocene to Quaternary sedimentary facies and stratigraphy of shallow-water contourite deposits in the Hupo Basin, East Sea of Korea

This study entails the characterization of the depositional environment of the Hupo Basin shelf. By means of sedimentary structure analysis, grain size, textures, sediment color, as well as optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) ages, a sediment core (19ESDP-101, 120 m) has been interpreted to be the product of shallow-water contourites. The shallow-water (165 m) contourite deposits observed in the core are divided into seven sedimentary facies grouped into four facies associations (FA): FA1) contourite drift, FA2) contourite drift/channel transition, FA3) contourite channel/drift transition, and FA4) contourite channel. FA1 resulted from the interaction between hemipelagic fallout, low-density gravity flow, and sedimentation under low velocity bottom currents. Compared to FA1, both FA 2 and FA3 are indicative of higher velocity bottom currents, owing to their relative increase in grain size and the presence of subtle indicators of bed-load transport. FA 4 portrayed massive to slightly bedded sand, representing a contourite channel environment with high-energy conditions. Fluctuations in the bottom current activity, related to the intensification and deceleration of the North Korean Cold Current (NKCC), have caused fluctuations between contouritic and hemipelagic-dominated periods. The vertical sedimentary facies stacking patterns observed at the Hupo Basin site suggested that, over time, the depositional processes changed at the site where the core was optained. The facies association stacking pattern suggests the lateral migration of the contourite depositional system and continuous flow of the NKCC. Our findings and interpretations can serve as a much needed reference for shallow-water contourite recognition in modern environments. Moreover, our proposed model can be used to more accurately interpret shallow-water contourite deposits.